Gamma interferon (IFN-gamma) expression was directed to the eyes of transgenic mice to investigate the possible role of this lymphokine in ocular pathogenesis. The most notable effect of IFN-gamma in these transgenic mice include micropthalmia, blepharophimosis, microphakia, impairment of lens fiber formation, arrest of retinal differentiation, retinal detachment, and persistent hyperplastic primary vitreous. Major histocompatibility complex (MHC) class II mRNA levels were significantly increased in the transgenic eyes, and MHC class II proteins were expressed in the cornea, iris, ciliary body, choroid, lens, and retinal pigment epithelium. Int-2/fibroblast growth factor (FGF)-3 expression was directed to the eye to investigate how the aberrant expression of this growth factor would affect the developmental program of the eye. The ectopic expression of int-2 during the embryonic development of the lens affected the differentiation of the entire eye, highlighted by the appearance of intraocular secretory glandular epithelium, similar to dermoid-like pathology.